Continuous Flow Operation

[Maple Hunter]

I recently upgraded to a 2x6 continuous flow evaporator that's manual operated. Trouble is I've never used one before and only have a rough idea of how to use it properly, rather than just doing batches. If someone could help me out that'd be great. Hope everyone's having a good season - sure started out that way here. Thanks.

[Ausable]

LOL - You are in for a whole new experience. I have a homemade 2 X 5 continuous flow evaporator and manually operated. Ya gotta have a feed tank - mine is an old fresh water tank from a camping trailer. I run a plastic tube from the feed tank with a small plastic valve on the end of the tube to control the flow at the first sap section of the sap pan. Your pans have to be level as you can get them. On starting your first boil flood all the sections with about 1 1/2 to 2 inches of sap and start you fire and boil and boil like you would on a batch pan and when the level starts to drop add some sap or get a trickle going in the first sap section to maintain a level you are comfortable with. As you boil away and add sap - you will eventually notice in your last syrup section of your syrup pan the sap is getting near syrup. Draw some off in your test cup and test with a maple syrup hydrometer. (as you probably know - lower your hydrometer carefully so it dosen't bounce off the bottom of your test cup and break) If you are close to syrup draw off a quart or two and test again. chances are on the new test from your syrup pan the syrup is too thin and needs more boiling. Once you draw off your first syrup on a manual system you have to pay attention to business - because the process will be repeated many times till you finish. -----You get the idea. Any more questions fire away ---- Hope I helped You some. --------Mike-----

[PerryW]

1) Keep adding sap to one end as necessary keep the level around 2" deep.

2) boil it like crazy

3) Draw syrup off the other end.

[Maple Hunter]

Thanks for the replies! It has two valves connecting the back pan to the front. I know there's two so direction can be reversed, but at what point do you open the vavle or do you crack it a certain amount to maintain levels?

[maple flats]

You will leave one valve open fully between the pans while boiling, the float will regulate the depth once adjusted correctly, switch valves when you reverse the flow. You will also need to change where sap enters the back pan at that time. You will draw off when it becomes syrup (7.1 degrees above hard boil of water). I try to run a continuous draw, even did with a 2x6. you need to barely open the valve and monitor the temp. Most draw small batches however. I find the continuous give more uniform gradients in the pans. I never attain long term constant draw but even with a 2x6 I sometimes drew for over and hour, but more frequently drew for 30-60 minutes.
After you get familiar with the rig, gradually reduce the pan depth until you are at 1". You will boil faster there but gain some experience first. Even in my 11th season, I run at 1" while my wife prefers almost 2".

[Maple Hunter]

Currently no float, so I'd have to do everything manually

[lpakiz]

By hand will work also. Use a tube size so that you can have a small stream coming out horizontally. It is easy to fine tune the flow by judging how far out or how short the stream "pees" out from the end. You can monitor with a depth gauge-as simple as a spoon lowered into the pan and noting where on the spoon is the selected depth. When you get close, you may not need to adjust more than every few hours, if you fire consistently.

[Brent]

the first stuff I read on firing an evaporator said to "open the door as infrequently as possible"

that meant letting the fire burn down and then filling with wood to the top.

That advice is backwards. The champions of continuous flow evaporators are oil fired. Continuous regular heat. So you do not want to let the fire burn down and cool off then pile in a couple armfuls of cold wood. That will cause it to die down even more and it will take several minutes to get up to heat again ... maybe even overshoot your desired stack temps. So in a rig that size, only add maybe 3 or 4 pieces every few minutes. I even lay mine down in front of the door so the radiant heat warms them for 5 minutes before I load them. It may sound silly but if you have a good fire you won't see any smoke at the top of the stack. If you through in a big pile of cold wood you'll see blackish smoke for quite a few minutes before you get hot and to the complete combustion stage. With the most stable heat levels, it will be much much easier to regulate the sap going in and the syrup going out.

If you are using raw sap at 2 to 2-1/2 percent, you'll likely be frustrated trying to get a continuous flow. I can get there now with a 2-12 x 8 rig with 7 to 9% sap going in. Regardless of your sap, a more steady high heat level will help. (and a good stack thermometer is a big help to. I got a digital pyrometer from Bartlett Instruments.)

[psparr]

the first stuff I read on firing an evaporator said to "open the door as infrequently as possible"

that meant letting the fire burn down and then filling with wood to the top.

That advice is backwards. The champions of continuous flow evaporators are oil fired. Continuous regular heat. So you do not want to let the fire burn down and cool off then pile in a couple armfuls of cold wood. That will cause it to die down even more and it will take several minutes to get up to heat again ... maybe even overshoot your desired stack temps. So in a rig that size, only add maybe 3 or 4 pieces every few minutes. I even lay mine down in front of the door so the radiant heat warms them for 5 minutes before I load them. It may sound silly but if you have a good fire you won't see any smoke at the top of the stack. If you through in a big pile of cold wood you'll see blackish smoke for quite a few minutes before you get hot and to the complete combustion stage. With the most stable heat levels, it will be much much easier to regulate the sap going in and the syrup going out.

If you are using raw sap at 2 to 2-1/2 percent, you'll likely be frustrated trying to get a continuous flow. I can get there now with a 2-12 x 8 rig with 7 to 9% sap going in. Regardless of your sap, a more steady high heat level will help. (and a good stack thermometer is a big help to. I got a digital pyrometer from Bartlett Instruments.)

I've found a similar feed method. I grab 2-3 pieces that I can hold in one hand and open the door with the other. I throw in the wood and close the door all in one quick motion adding wood every 2 minutes or so. That's when I'm not busy of course.

[maple flats]

With a 2x6 I'd suggest you fuel it every 7 minutes if natural draft. If you sometime add forced draft or better yet "air over fire" the times will change. For now, add at 7 minutes by a timer. Fuel 1/2 as fast as is reasonable and close the door. next time fuel the other half. Only fill the firebox to about 6-7" below the pans. The biggest thing to remember, the wood must be dry and should be split to about wrist size.